Reinforced plastic article



June 26, 1951 P. A. NORRIS REINFORCED PLASTIC ARTICLE Filed March 15,1946 INVENTOR Paul A. A/orrze junta 2, i951 REINFORCED PLASTIC ARTICLEPaul A. Norris, Dayton, Ohio, assignor to General Motors Corporation,Detroit, Mich a corporation of Delaware Application March 15, 1946,Serial No. 654,779

1 Claim. 1

This invention relates to plastics and is particularly concerned withlaminated plastics which have high impact resistance and are tough andflexible.

It is an object of the invention to provide a composition and method formaking a laminated plastic article wherein the article has high impactstrength, a reasonable degree of flexibility and a durable heatresistant and moisture resistant surface.

In carrying out the above object, it is a further object to provide acomposition for and method of making large sheets of laminated plasticmaterial, which has a low tendency toward shrinkage in the mold wherebysatisfactory moldings can he made in relatively short curing periods.

A still further object of the invention is to provide a composition forand method of making a laminated plastic article with high resistancetoward impact stress wherein the laminate, or cloth sheeting material,is sealed by a plastic wetting agent which, when dried, presents a verythin sealing coat over the laminate and which prevents ingress ofanother plastic that forms the main body of the laminated article, whichlater plastic has high strength and is of a semi-rigid character.

In carrying out the above object it is a further object to seal thecloth sheeting material with a carboxy or hydroxy methyl cellulose inwater solution.

Further objects and advantages are apparent, reference being had to theaccompanying drawing wherein a preferred object of the invention isclearly shown.

In the drawings:

Fig. 1 is a cross section on a greatly enlarged scale of the clothlaminating material.

Fig. 2 is a similar view wherein the cloth has been sealed with thesealing coat described in detail hereinafter.

Fig. 3 is a cross section of one strand of the cloth in Fig. 2, on aneven larger scale, showing the penetration of the sealing materialwherein the concentration thereof is reduced toward the center of eachstrand, but is suflicient to form a complete coating of the outersurface of the strand;

Fig. 4 is a view in cross section on a greatly enlarged scale and showsa sectional view of the laminatedplastic article wherein the sealedcloth laminate is embedded in the plastic.

In the manufacture of large surface, relatively thin articles, such asdoor panels and the like, it has always been desirable to form such apanel of a material that has thcrmosetting properties but which may bepoured into the mold in liquid form and cured in a relatively short timeand wherein the panel may be removed hot from the mold with asatisfactory smooth surface thereon together with reasonableflexibility, toughness and great strength and resistance toward impactblows. Such material heretofore has been unknown since, when the moldingis made, the basic resin, or plastic, used impregnates completely thecloth reenforcemcntor laminate which rigidly holds the cloth so that itis easily sheared by impact blows whereby the article is unsatisfactoryfor its intended use. Further, when the article is removed from the moldhot and/or when the article is cured in a relatively short time throughthe use of catalysts in the compound, great shrinkage occurs, which ifthe article is flanged and includes re-entrant angles thereon will causebreakdown of the panel if there is no relief for the shrinkage wherebythe article becomes distorted and is usually cracked at the cornerportion thereof, thereby making it unusable.

This invention is, in the main, directed to the solution of these pastproblems in. a satisfactory manner whereby large sections of sheetmaterial havingflanged portions thereon may be manu-r factured withgreat ease and in an expeditious manner. These articles aresubstantially free from shrinkage cracks or distortion and may beremoved from the mold while hot. Furthermore the articles may be curedin a relatively short time and while reasonably flexible and tough havehigh resistance toward impact blows and withal are commerciallyeconomical from a manufacturin'g standpoint.

In connection with door panels, I have found that the base materialtherefor is preferably an alkyd polyester reacted witl'rvinyl benzene orany other easy polymerizable hydrocarbon, for example, vinyl benzene,di-vinyl benzene, combinations thereof etc. The alkyd polyesters may beformed as is well known in the art by the reaction of polybasic acids oranhydrides thereof with polyhydric alcohols, such as members of theglycol family. I have found that phthalic anhydride reacted withglycerol forms a satisfactory alkyd polyester which may be reacted withvinyl benzene in suitable proportions to obtain the desired plasticityand ultimate physical characteristics.

In place of phthalic anhydride, phthalic acid, maleic acid, maleicanhydride, succinic acid, adipic acid, anhydrides thereof, or in factany of the polybasic acids are satisfactory, together coating thereoverof the external surfaces.

3 with any polyhydric alcohol such as, lycerol, ethylene glycol or anyother glycol.

The reaction between the polybasic acid and polyhydric alcohol proceedsprimarily as a condensation reaction. The second reaction between thealkyd polyester and the polymerizable hydrocarbon probably occurs withsome cross linkage between the compounds.

During the cure, the resin probably sets up through polymerization andmechanical vulcanization and substantially loses its thermoplasticproperties and becomes thermosetting in character. Mechanicalvulcanization may be explained by an intermingling of the molecularfibers which cause mechanical cross bonding.

The reaction product of the alkyd polyester and the polymerizablecompound forms a liquid vulcanizable alkyd resin which may be preservedby the addition of small quantities of guiacol, etc. that acts solely asan inhibitor against at mospheric setting up of the compound. Quantitiesin the order of 2% guiacol are usuallysatisfactory.

In practice I use equal proportions of the alkyd. polyester and vinylbenzene to which is added approximately 20% by weight of a filler whichmay be a pigment per se or may contain a pigment, for example, 20% byweight of the plastic component of titanium dioxide may be used. In thisinstance 2% titanium dioxide yields a satisfactory color and theremaining 18% acts solely as a filler which reduces the shrinkage asnoted hereinbefore. In place of titanium dioxide, the filler portion maybe silica dioxide or any other inert material. In this connection thequantity thereof to be used should be equivalent in volume to the volumeof titanium dioxide in the quantities noted. In certain instances thequantities of the filler may reach 50% by weight of the plasticingredient (for TiO2) but obviously in this case the strength of thearticle and its flexibility will be reduced. Therefore, for a door panelor other similar article I prefer to use in the order of 20% by weight.It is apparent that other materials yielding desired properties may beused as satisfactory substitutes.

In the manufacture of the panel, the laminate, or cloth sheeting used asa reenforcement is sealed prior to its introduction into the mold andthis sealing may be accomplished in one embodiment by dipping the clothin a water solution of a carboxy or hydroxy-methyl cellulose methylcellulose derivative, 90% water). The laminate impregnated with themethyl cellulose derivative is then dried, whereby the major portion ofthe im-pregnant is evaporated since this portion is water. After dryingit will be found that the methyl cellulose derivative impregnates eachfiber of the cloth with a complete This coating prevents introductioninto the cloth of the alkyd resin to be applied in the mold. Thissealing process performs two very important functions, first and mostimportant, the hydroxy or carboxy methyl cellulose compound is tough andhighly flexible and is a good wetting agent, and after impregnation intothe cloth, the cloth is still flexible and is diflicult to tear andobviously due to its flexibility has high resistance to impact blows.Thus, upon impregnation with the more rigid plastic, the sealed clothfibers do not soak up any of the more rigid plastic whereby theirresistance toward impact is not in any way reduced. In this instance ifthe fibers soaked up the more rigid plastic material they would easilybe sheared upon impact blows.

The second factor in favor of the use of sealing compound revolvesaround the economy of the operation. The plastic utilized in themainbody of the article is a relatively expensive compound compared to themethyl cellulose derivative and since of the sealing solution is water,very little sealing compound is utilized. Thus when the fiber isimpregnated and sealed it does not tend to soak up the more expensiveplastic and thereby reduces the cost of the finished article, whileproducing a reasonably flexible, tough and strong article.

In the manufacture of articles from the material described herein, themold is filled with a catalyzed charge of the vulcanizable alkyd resin.On this is laid a sealed section of cloth material. The mold is closedand the plastic is vulcanized or cured for from one to five minutes at220 F. The time and temperature may be varied to fulfill manufacturingnecessities, although the time and temperature noted is preferred. Aftercuring, themold is opened and the plastic article may be removed hottherefrom.

In order to catalyze the already inhibited plastic, two parts of acobalt soap, such as cobalt napthanate or cobalt resinate, for example,is used together with 1.5 parts by weight of a peroxide such as benzoylperoxide. These two compounds counteract the guiacol inhibitorpreviously added and will cause a setting up of the compound in thepresence of air if suflicient time is given. I have found that from .1part to 4 parts of the catalyst by weight may be used with varyingcuring times and temperatures.

The use of the filler as previously explained prevents or reducesshrinkage of the plastic upon curing and the use of the sealing compoundimproves the physical characteristics of the finished article. Thesefactors are the principal reasons for the success of this inventionwhereby satisfactory panels and other large surface articles may bemanufactured which have the desired physical characteristics.

In some cases it may be desirable to waterproof the laminate which maybe accomplished by insolubilizing the methyl cellulose derivative. Thismay be done by adding glyoxal dialdehyde in small quantities, preferablyless than 1%, depending upon the results desired.

It is apparent that the sealing method disclosed herein may be practicedwith other seal ing plastics and other molding plastics instead ofthosedescribed. For example, for a sealing coat, polymerized butyrallatex, flexible water soluble alkyd resins, or other liquid compounds ofhigh flexibility are suitable. For the main body portion of the materialin place of an alkyd resin, any other well known resin may be used andif thermosetting properties are not desired, thermoplastics may be used.For example, polyvinyl chloride, methyl methacrylate, phenolic resins,urea resins, etc.

The drawing shows cross sections of the various material wherein Fig. lis a cross section of the laminate where the warp and woof aredesignated by numerals 20 and 22 respectively. It Fig. 2 the sealingcompound is shown covering the threads 20 and 22 as at 24 and 26respectively. This sealing compound, as noted, impregnates andcompletely coats each fiber as shown in an enlarged cross section ofsingle thread or fiber in Fig. 3. A finished article 30 is shown in afragmentary sectional view in'Fig. 4 where the 5 reinforced resin isdesignated at 32. This resin makes up the body of the article which isreinforced by the fabric designated at 20' and 22, which fabric iscoated with the sealing compound 24.

While the embodiments of the present invention constitute preferredforms, it is to be understood that other forms might be adopted, allcoming within the scope of the claim which follows.

What is claimed is as follows:

A new article of manufacture, comprising a reinforced plastic sheetwhich is semi-rigid and strong at room temperature, said plastic sheetconsisting of a laminate of cloth which, prior to its incorporation inthe sheet, has been sealed with hydroxy methyl cellulose which coats thecloth and is impregnated therein, and a resin impregnated into andcompletely covering said sealed laminate, said resin consisting of thereaction product of an alkyd poly-ester and vinyl benzene, said sheethaving high impact resistance and reasonable flexibility.

PAUL A. NORRIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

